Sharif Digital Repository

This paper employs the framework of value-based seismic design to optimize the geometrical and mechanical properties of lead rubber bearings (LRBs). An optimization problem is proposed within this framework. Construction cost and seismic consequences are chosen as the value components. Most failure modes of the LRB, such as strength deterioration, axial buckling, and rubber rupture, have been carefully considered in the seismic response. Besides, a new cost function for LRBs is developed from actual isolated building projects. Moreover, the minimum code requirements for lead rubber isolated buildings are formulated as the design constraints. FEMA P-58 methodology is exploited to predict the... 

This paper uses the value-based seismic design methodology to optimize the mechanical and geometrical properties of triple friction pendulum bearings (TFPBs). An optimization procedure is proposed within this methodology. Initial construction cost and lifetime seismic losses are picked as the value components. Extreme failure conditions of the TFPB, less considered in the current literature, such as the uplift and exit failure modes of the curved surface sliders at the end edges, have been carefully considered in the seismic behavior of the structure. Besides, the minimum code provisions and practical limitations (e.g., the critical overturning diameter of sliders) for friction pendulum... 

Endurance time method is a dynamic analysis in which structures are subjected to increasing excitations. These excitations are generated to be compatible with ground motions. Conventional excitation generating processes take into consideration the dynamic characteristics related to intensity and frequency contents of ground motions; however, duration-related characteristics have never been considered directly. In this study, the existing methodology is extended to include Cumulative Absolute Velocity as a duration-related parameter in the generating process. These newly generated excitations are then employed to estimate nonlinear responses of three concrete structures as case studies.... 

Recent studies showed that while code-compliant structures can generally protect the safety of the occupants, they may exhibit extensive damages during strong earthquake events. On the other hand, structures are generally designed to satisfy the seismic code requirements with the least initial cost regardless of their life cycle cost. In recent years, value-based design has been considered as an effective alternative for code-based design procedures. In this method, as well as the initial cost of the structure, a comprehensive consequence modeling is performed in the design process. In this paper, for the first time, a value-based design optimization method is developed for seismic... 

The aim of this study is to develop a new simulation procedure of endurance time excitations in which hysteretic energy compatibility is included. Existing methods for simulating excitations consider only amplitude and frequency content of motions and disregard parameters related to cumulative damage of structures. Hysteretic energy consistency, as a cumulative damage-related parameter, is included in the process. The proposed method is applied to generate new excitations. Efficiency of the proposed method is examined in two ways: (1) comparing damage spectra of simulated excitations with recorded ground motions; (2) applying simulated excitations in seismic assessment of three concrete... 

The existing loss assessment frameworks in the literature are mainly limited to the evaluation of the expected lifetime seismic losses, and do not assess the probability distribution of the long-term losses. The long-term loss is defined as the cumulative seismic loss of the structures over the service life. However, the probability distribution of the long-term losses can also be informative for decision-making under uncertain seismic consequences. This paper proposes an efficient procedure to calculate the probability distribution of the long-term losses. The procedure is based on the discretization of continuous random variables and performing two sets of recursive convolutions. The... 

A framework for optimal seismic design of structures, considering maximum value as the design objective, is introduced. In this framework, the value parameter incorporates a comprehensive set of performance indicators. Decision indicators are mapped into equivalent economic values and are directly involved in the design process. This approach leads to optimal assignment of the available resources to meet infrastructure requirements. The construction cost and the risk of seismic consequences are considered as the value components. FEMA-P58 methodology is utilized in estimation of the seismic consequences including the repair cost, repair time, injuries and casualties. Endurance Time method is... 

The value-based seismic design framework is a new design method that efficiently balances the construction resources and the seismic consequences, through reliable evaluation of the building performance at an affordable computational cost. This paper employs the value-based design approach to optimize the cross-section proportions of the steel wide-flange members. An optimization problem is proposed within the framework of value-based design. Construction cost and seismic consequences are selected as the value components. Moreover, the minimum code requirements are formulated as the design constraints. FEMA-P58 framework is exploited for the prediction of the seismic consequences including... 

The endurance time method is a time history dynamic analysis in which structures are subjected to predesigned intensifying excitations. This method provides a tool for response prediction that correlates structural responses to the intensity of earthquakes with a considerably less computational demand as compared to conventional time history analysis. The endurance time method is being used in different areas of earthquake engineering, such as performance-based assessment and design, life-cycle cost-based design, value-based design, seismic safety, seismic assessment, and multi-component seismic analysis. Successful implementation of the endurance time method relies heavily on the quality of... 

A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network... 

Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the... 

With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost... 

Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing... 

A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring... 

We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems. The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity. The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction. This signifies the potential of GT as a biocompatible matrix for... 

The Class-E power amplifier has been widely studied and formulated in the literature. Although the majority of reported inductive coupling wireless power transfer (WPT) systems use a class-E power amplifier for driving the primary coil, still there is a lack of a comprehensive study on class-E circuit dedicated to WPT, providing a set of closed form design equations for proper class-E operation. This paper presents the required design equations needed to design a 'true' class-E circuit for WPT applications. Equations for the series-tuned secondary coil WPT system are presented, as well as two different design procedures for the parallel-tuned secondary coil. The derived equations have been... 

Pole Side Impact Tes is one out of three crash tests described by Euro NCAP standard for star rating of a vehicle and is required for assessing the Adult Occupant Protection. In this paper the goal is to determine the crashworthiness of side doors and B pillar in a Pole Side Impact Test based on Euro New Car Assessment Program (Euro-NCAP) using computer and simulation method. In this matter, a vehicle model has been prepared and meshed using Hypermesh and CATIA. The velocity of 29 km/h has been assigned to the vehicle which was on top of a cart while the pole has been assigned as a rigid static object based on Euro NCAP requirements specifically. Results show that different amounts of energy... 

To assess a car under the Euro New Car Assessment Program (Euro-NCAP), Adult Occupant Protection is one out of three parameters which need to be calculated with a weight factor of 50% while the other parameters, Child Occupant Protection and Pedestrian Occupant Protection, have a weight factor of 20%. The Pole Side Impact Test, beside two other tests, Side and Front Impact, is also required to calculate the Adult Occupant Protection. It shows how important the Pole Side Impact Test is and what an effective role it has in the car rating assessment. In this paper, the objective is to evaluate the effect of thickness on the energy absorbed by the side doors and the B pillar and its...